1. Field of the Invention
The present invention relates to a fiber cord or rope which is suitable for use as a mooring rope for ships, and particularly to a fiber cord of triple-braided structure.
2. Description of the Prior Art
A cord of double-braided structure is known which has been conventionally utilized as a mooring rope for ships. This structure is constituted by a core which is formed by knitting and braiding a plurality of strands, each comprising one or more of fiber filaments or yarns, and by an outer layer which is formed by knitting and braiding a plurality of strands to surround the core. Each filament which forms such a rope has been only a nylon fiber or a Tetoron fiber which is a well known polyethylene terephthalate fiber available from Toray Corp., Japan. However, since this fiber has high elongation and low tensile strength, cords which are formed by such a fiber do not show high tensile strength.
Recently, a polyaramid fiber which has remarkable low elongation and high tensile strength as compared with nylon or Tetoron fibers has been developed and utilized as a cord element. The elongation in breaking of the polyaramid fiber is much lower than that of the nylon or Tetoron fiber: the elongation at break of the polyaramid fiber is about 6%, while the elongation at break of the nylon or Tetoron is about 20%. Therefore, it was contemplated that cords of extremely high strength could be formed by utilizing the polyaramid fiber.
However, according to the experience of the present inventor, it has been confirmed that if a cord of double-braided structure is constituted by a fiber such as the polyaramid fiber which has high strength and low elongation, the obtained cord may be stiff as a whole and may not be flexible, thus considerably increasing its fatigue by bending.